[AlphaCommerceHub] What is the difference between the «AlphaHPP» and «API Integration Guide» documentation sections?

• The «AlphaHPP» section describes AlphaHPP. It is a PayPal-like approach to handle payments: a customer is redirected to a payment service provider’s payment page.
• The «API Integration Guide» section describes direct server-to-server API calls without customer redirection:

This integration guide is specifically tailored to the direct AlphaHub integration.
For the APC hosted payment page service a separate integration guide is available.